The passenger compartment of motor vehicles provides a space which is environmentally adjustable to suit the predilections of the passengers via a heating, ventilation and air conditioning system, hereinafter simply referred to as an HVAC system. In this regard, FIGS. 1 and 2 are schematic depictions of aspects of a conventional HVAC system 10 of a motor vehicle.
As shown at FIG. 1, the HVAC system 10 includes an HVAC module 10a which, in turn, includes a heater core 12 and an evaporator core 14, both of which serving to provide conditioned air to the passenger compartment 16 of the motor vehicle. The heater core 12 conditions the air by heating it as it passes therethrough to the passenger compartment 16 via heated coolant passing therein, wherein the coolant is heated by the internal combustion engine 18, cooled by a radiator 20, and temperature regulated by a thermostat 22. The evaporator core 14 conditions the air by cooling it as it passes therethrough to the passenger compartment 16 via cooled refrigerant passing therein, wherein the refrigerant is compressed by a compressor 24, the heat of compression is rejected to the atmosphere by a radiator 26, and then cooled thereafter by an expansion process. In either case, the temperature of the air entering the passenger compartment is user selectable.
Referring next to FIG. 2, the HVAC module 10a is depicted, the module being defined by an enclosing sidewall 28. Air input is provided thereto, either via a first air-in path 30 which provides air outside the motor vehicle, or a second air-in path 32 which provides air recirculated with respect to the passenger compartment, selection of which of the first and second air-in paths being determined by an air-in door 34. A blower 36 causes air to be drawn in from the first and second air-in paths, and blown air 38 is passed downstream therefrom to the evaporator core 14. A temperature door 40 is positioned to cause the blown air to pass entirely or partly through the heater core 12 or to entirely by-pass it in the event the air conditioning is on maximum. A series of downstream vent doors then direct how the conditioned air passes into the passenger compartment, for example via a floor vent door 42 of a floor vent 42a, and a panel/windshield vent door 44 of a panel vent 44a and a windshield (defroster) vent 44b. 
During a typical air conditioning operation of an HVAC system, the evaporator core 14 cools the air which is blown over the evaporator tubes. As the air passes through the evaporator core, it becomes cooler and drier due to loss of moisture content. Usually, the moisture captured from air accumulates on the evaporator core surface and flows down and out via a drain tube 46. However, not all of the accumulated liquid leaves the evaporator core, depending upon the amount of moisture and the environmental conditions, most notably in high temperature and high humidity environments. Water retention at the evaporator core can be problematic, as the accumulated moisture could result in passengers sensing humidity from air entering through the vents, smelling odor due to bacteria and microbial growth, and, from a mechanical point of view, there is potential for rusting of the evaporator core. Accordingly, it is very desirable to ensure this accumulated water at the evaporator core is vacated therefrom whenever the motor vehicle is turned off.
Current HVAC system practices operate the blower intermittently for a short period of time after engine shut-down to remove as much moisture as possible (according to a “blow algorithm” that is well known in the HVAC system art). The blow algorithm directs the blower to blow air across the whole evaporator core surface area at the same time, which means that the air stream speed of the blow air is low and, as a result, could possibly not remove all of the moisture out of the evaporator core before blower shut-down. In addition, the moisture removal rate is limited by the vehicle's battery voltage and is potentially ineffective in humid environments. Accordingly, it is sometimes necessary to use UV light at the evaporator core to get rid of the bacterial growth, the source of which light having attendant packaging, cost and service issues.
Accordingly, what remains needed in the art is an efficient and effective way to ensure removal of moisture from the evaporator cores of HVAC systems.